Ramona Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ramona Observatory clear sky chart from 2005-11-05 to 2017-09-17.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
73%
16239
32%
46981
28%
16197
76%
16197
47%
24751

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
65%
716
29%
2324
28%
716
71%
716
40%
1209
January16th to endNight
62%
768
33%
2304
28%
768
70%
768
37%
1303
February1st to 15thNight
66%
698
33%
2112
31%
698
72%
698
41%
1138
February16th to endNight
56%
632
27%
1895
29%
632
58%
632
30%
1160
March1st to 15thNight
65%
720
28%
2158
30%
720
69%
720
39%
1204
March16th to endNight
70%
768
28%
2040
25%
768
72%
768
41%
1201
April1st to 15thNight
63%
719
26%
1799
18%
719
65%
719
41%
1111
April16th to endNight
68%
720
29%
1800
18%
720
70%
720
48%
1042
May1st to 15thNight
69%
581
28%
1661
20%
581
70%
581
43%
943
May16th to endNight
67%
561
26%
1685
20%
561
68%
561
39%
962
June1st to 15thNight
77%
540
27%
1620
24%
540
78%
540
50%
840
June16th to endNight
91%
540
35%
1620
31%
540
91%
540
76%
640
July1st to 15thNight
88%
510
26%
1530
22%
510
88%
510
59%
710
July16th to endNight
88%
629
29%
1653
22%
591
87%
591
53%
845
August1st to 15thNight
90%
717
33%
1790
21%
713
90%
713
72%
848
August16th to endNight
92%
764
39%
1910
28%
764
92%
764
70%
933
September1st to 15thNight
89%
720
35%
1875
29%
720
89%
720
65%
915
September16th to endNight
85%
664
44%
1837
42%
664
87%
664
70%
819
October1st to 15thNight
75%
660
35%
1815
33%
660
77%
660
52%
940
October16th to endNight
74%
704
36%
2102
36%
704
77%
704
47%
1068
November1st to 15thNight
78%
700
33%
2275
37%
700
80%
700
49%
1075
November16th to endNight
72%
720
34%
2340
35%
720
76%
720
43%
1171
December1st to 15thNight
65%
720
31%
2340
32%
720
69%
720
37%
1273
December16th to endNight
59%
768
31%
2496
28%
768
66%
768
34%
1401

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
5%312213346%65%
47788
Night
6%413313346%61%
47182
TransparencyDay
21%36%15%25%27%
47489
Night
23%37%14%22%28%
46982
SeeingDay
7%8%29%38%12%3
5916
Night
7%210%31%36%11%
16252

By Month

Percentage Cloud Cover SW (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
9%423312345%59%
1613
16th to endDay
11%413313346%55%
1920
February1st to 15thDay
9%313324435%57%
1751
16th to endDay
14%5%24424447%44%
1579
March1st to 15thDay
7%42321335%9%56%
1800
16th to endDay
6%313323347%58%
2181
April1st to 15thDay
7%424324346%55%
2149
16th to endDay
6%312212346%66%
2160
May1st to 15thDay
6%313313336%63%
2289
16th to endDay
5%413213235%66%
2429
June1st to 15thDay
4412222225%69%
2340
16th to endDay
1111112383%
2340
July1st to 15thDay
131231235%7%67%
2340
16th to endDay
22221336%9%65%
2399
August1st to 15thDay
11221222477%
2160
16th to endDay
111212235%76%
2292
September1st to 15thDay
1112212335%75%
2085
16th to endDay
12111123379%
1828
October1st to 15thDay
5%314323245%63%
1815
16th to endDay
6%41311222369%
1766
November1st to 15thDay
5%212223345%65%
1584
16th to endDay
7%323212447%61%
1620
December1st to 15thDay
9%413413349%53%
1620
16th to endDay
14%413323436%53%
1728
January1st to 15thNight
7%313323446%58%
2324
16th to endNight
11%413313346%56%
2304
February1st to 15thNight
8%323312345%60%
2101
16th to endNight
13%5%3442334448%
1895
March1st to 15thNight
8%5%14314347%54%
2158
16th to endNight
7%5%1332445%9%52%
2040
April1st to 15thNight
9%7%2331335%7%52%
1799
16th to endNight
7%6%23213236%59%
1800
May1st to 15thNight
6%7%13423249%53%
1661
16th to endNight
7%8%24313346%54%
1684
June1st to 15thNight
36%24313337%59%
1620
16th to endNight
111112136%78%
1620
July1st to 15thNight
1313213346%67%
1620
16th to endNight
21322445%8%63%
1766
August1st to 15thNight
1211212249%70%
1800
16th to endNight
22112246%74%
1910
September1st to 15thNight
222222336%71%
1875
16th to endNight
22111122379%
1837
October1st to 15thNight
5%313322337%65%
1815
16th to endNight
5%413312335%63%
2102
November1st to 15thNight
431221333468%
2275
16th to endNight
6%423313335%62%
2340
December1st to 15thNight
9%424323447%54%
2340
16th to endNight
13%423323346%54%
2496

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
27%25%12%24%26%
1614
16th to endDay
30%47%13%17%28%
1920
February1st to 15thDay
28%45%13%22%26%
1751
16th to endDay
39%46%13%22%13%
1579
March1st to 15thDay
26%36%17%23%23%
1800
16th to endDay
26%49%21%23%15%
2181
April1st to 15thDay
29%37%22%26%10%
2149
16th to endDay
19%37%22%27%19%
2160
May1st to 15thDay
22%46%18%27%20%
2289
16th to endDay
20%36%20%35%13%
2432
June1st to 15thDay
18%25%15%27%29%
2340
16th to endDay
7%146%21%59%
2340
July1st to 15thDay
14%37%11%23%39%
2201
16th to endDay
15%5%12%21%27%17%
2249
August1st to 15thDay
10%26%12%33%33%
2146
16th to endDay
12%26%11%34%33%
2292
September1st to 15thDay
13%25%11%31%35%
2085
16th to endDay
11%148%33%41%
1828
October1st to 15thDay
22%3415%26%26%
1815
16th to endDay
20%2410%20%41%
1766
November1st to 15thDay
21%26%12%21%34%
1584
16th to endDay
23%35%12%20%34%
1620
December1st to 15thDay
29%38%15%16%25%
1620
16th to endDay
33%46%15%22%17%
1728
January1st to 15thNight
26%45%12%21%29%
2324
16th to endNight
31%37%10%15%31%
2304
February1st to 15thNight
27%36%13%21%28%
2112
16th to endNight
37%45%13%21%17%
1895
March1st to 15thNight
29%36%17%18%23%
2158
16th to endNight
27%6%7%18%22%17%
2040
April1st to 15thNight
31%48%20%23%12%
1799
16th to endNight
25%38%18%20%22%
1800
May1st to 15thNight
26%5%9%15%22%20%
1662
16th to endNight
28%5%7%18%22%16%
1685
June1st to 15thNight
21%48%13%25%25%
1620
16th to endNight
7%16%6%18%58%
1620
July1st to 15thNight
15%38%9%23%39%
1530
16th to endNight
16%7%10%20%28%16%
1653
August1st to 15thNight
8%49%15%31%30%
1790
16th to endNight
11%36%12%29%36%
1910
September1st to 15thNight
13%37%11%28%35%
1875
16th to endNight
11%139%32%40%
1837
October1st to 15thNight
21%36%15%27%25%
1815
16th to endNight
23%249%19%40%
2102
November1st to 15thNight
20%35%13%19%37%
2275
16th to endNight
24%35%13%19%33%
2340
December1st to 15thNight
29%47%14%18%25%
2340
16th to endNight
32%39%12%18%22%
2496

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
30%320%36%8%
92
16th to endDay
15%12%35%29%5%1
288
February1st to 15thDay
9%12%36%30%10%
266
16th to endDay
16%17%34%23%7%
238
March1st to 15thDay
9%16%30%28%10%4
270
16th to endDay
6%15%35%28%11%2
288
April1st to 15thDay
9%17%38%23%9%1
269
16th to endDay
7%17%41%24%5%3
270
May1st to 15thDay
14%10%35%30%7%2
288
16th to endDay
9%10%35%32%9%1
330
June1st to 15thDay
46%32%37%16%3
315
16th to endDay
1123%46%19%7%
315
July1st to 15thDay
215%53%20%6%
305
16th to endDay
48%57%18%10%
327
August1st to 15thDay
119%53%16%8%
315
16th to endDay
112%59%17%8%
332
September1st to 15thDay
2128%51%12%3
315
16th to endDay
36%32%43%10%3
260
October1st to 15thDay
411%42%30%9%1
255
16th to endDay
8%6%33%33%15%2
212
November1st to 15thDay
5%424%31%30%4
90
16th to endDay
15%5%28%34%14%1
90
December1st to 15thDay
4418%42%25%4
90
16th to endDay
19%6%27%33%13%
96
January1st to 15thNight
7%217%35%24%11%
720
16th to endNight
13%215%35%25%7%
768
February1st to 15thNight
11%212%36%26%9%
704
16th to endNight
14%316%36%21%6%
632
March1st to 15thNight
10%214%38%27%5%
720
16th to endNight
7%310%38%30%8%
768
April1st to 15thNight
10%413%39%24%6%
719
16th to endNight
8%413%35%29%8%
720
May1st to 15thNight
7%213%36%31%7%
582
16th to endNight
7%412%33%36%5%
563
June1st to 15thNight
4110%39%38%6%
540
16th to endNight
1233%53%8%
540
July1st to 15thNight
317%67%10%
510
16th to endNight
21113%63%17%
629
August1st to 15thNight
318%57%19%
717
16th to endNight
1111%57%28%
764
September1st to 15thNight
1418%57%17%
720
16th to endNight
26%29%45%15%
664
October1st to 15thNight
6%210%36%34%10%
660
16th to endNight
7%18%31%32%18%
704
November1st to 15thNight
6%9%37%33%12%
700
16th to endNight
8%111%34%28%16%
720
December1st to 15thNight
11%213%35%25%10%
720
16th to endNight
15%316%32%24%8%
768
Page generated at 2017-09-18 05:38:20. Version ac04

Copyright 2017 A. Danko


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